Perfluoroelastomers (elastomeric perfluoropolymers) are polymeric materials which exhibit outstanding high temperature tolerance and chemical resistance. Consequently, such compositions are particularly adapted for use as seals and gaskets in systems in which elevated temperatures and/or corrosive chemicals are encountered. The outstanding properties of perfluoropolymers are largely attributable to the stability and inertness of the copolymerized perfluorinated monomer units which make up the major portion of the polymer backbone, e.g., tetrafluoroethylene and perfluoro(alkyl vinyl) ethers. In order to completely develop elastomeric properties, perfluoropolymers are typically crosslinked, i.e. vulcanized. To this end, a small percentage of cure site monomer is copolymerized with the perfluorinated monomer units. Cure site monomers containing at least one nitrile group, for example perfluoro-8-cyano-5-methyl-3,6-dioxa-1-octene, are especially preferred. Such compositions are described in U.S. Pat. Nos. 4,281,092 and 4,394,489; and in International Application WO 95/22575.
A recently-developed class of perfluoroelastomers having carbonyl-containing functional groups is disclosed in co-pending U.S. patent application Ser. No. 08/755,919, entitled "Fast-curing Perfluoroelastomer Compositions", filed Nov. 25, 1996. These polymers are characterized by having carbonyl-containing functional groups, including carboxyl groups, carboxylate groups, carboxarnide groups, and mixtures thereof. Preferably, the carbonyl-containing functional groups are endgroups generated as a result of persulfate initiation of the polymerization reaction and the reaction is carried out in the absence of sulfite or bisulfite reducing agents. The carbonyl-containing perfluoroelastomers exhibit outstanding cure characteristics but they are difficult to process in certain end-uses because of their relatively high viscosity. A method for decreasing viscosity of the carbonyl-containing perfluoroelastomers would permit use of these materials in a wider variety of end-use applications.